This book deals with the Islamic law of will for the administration of Muslim estates. It examines the rules of Islamic law of wills in Malaysia in respect of testamentary provisions giving directions as to the administration of the estates and other matters. This is done in the context of the will of entrustment (wisoyah) in particular. The discussion focuses on the meaning of will of entrustment (wisoyah) its origin, its characteristics, its legality, its legal ruling and its creation which deal with four essential elements: testator (musi), executor (wasi), subject matter of will (musa fih) and formation (sighah). The discussion will also highlight the issues of testacy and intestacy with regard to Muslim estates. In what sense are these two terms to be taken by Muslims? The study attempts to examines various state enactments relating to Islamic law of wills. This requires some reference to the meaning of Islamic wills as understood at present and wills under civil law.